"They were providing food to hungry civilians in the middle of a war. They were brave and selfless. Their deaths are a tragedy," Biden said in a statement on Tuesday.

The seven WCK workers, who died in an Israeli strike on Monday, were from Australia, Poland, the UK, a dual citizen of the US and Canada, and Palestine. They were travelling in a deconflicted zone in two armoured cars and a soft-skinned vehicle, WCK said in a statement.

The WCK convoy was hit as it was leaving the Deir al-Balah warehouse, where the team had unloaded more than 100 tons of humanitarian food aid brought to Gaza on the maritime route, it added.

"Israel has pledged to conduct a thorough investigation into why the aid workers' vehicles were hit by airstrikes. That investigation must be swift, it must bring accountability, and its findings must be made public," the US President said.

"Even more tragically, this is not a stand-alone incident. This conflict has been one of the worst in recent memory in terms of how many aid workers have been killed. This is a major reason why distributing humanitarian aid in Gaza has been so difficult – because Israel has not done enough to protect aid workers trying to deliver desperately needed help to civilians," he added.

Bident further said that the US will continue to do all "we can to deliver humanitarian assistance to Palestinian civilians in Gaza, through all available means".

"I will continue to press Israel to do more to facilitate that aid. And we are pushing hard for an immediate ceasefire as part of a hostage deal. I have a team in Cairo working on this right now," he said.